// This optional code is used to register a service worker.
// register() is not called by default.

// This lets the app load faster on subsequent visits in production, and gives
// it offline capabilities. However, it also means that developers (and users)
// will only see deployed updates on subsequent visits to a page, after all the
// existing tabs open on the page have been closed, since previously cached
// resources are updated in the background.

// To learn more about the benefits of this model and instructions on how to
// opt-in, read https://bit.ly/CRA-PWA

const isLocalhost = Boolean(
  window.location.hostname === 'localhost' ||
  // [::1] is the IPv6 localhost address.
  window.location.hostname === '[::1]' ||
  // 127.0.0.1/8 is considered localhost for IPv4.
  window.location.hostname.match(
    /^127(?:\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)){3}$/,
  ),
);

export function register(config) {
  if (process.env.NODE_ENV === 'production' && 'serviceWorker' in navigator) {
    // The URL constructor is available in all browsers that support SW.
    const publicUrl = new URL(process.env.PUBLIC_URL, window.location.href);
    if (publicUrl.origin !== window.location.origin) {
      // Our service worker won't work if PUBLIC_URL is on a different origin
      // from what our page is served on. This might happen if a CDN is used to
      // serve assets; see https://github.com/facebook/create-react-app/issues/2374
      return;
    }

    window.addEventListener('load', () => {
      const swUrl = `${process.env.PUBLIC_URL}/service-worker.js`;

      if (isLocalhost) {
        // This is running on localhost. Let's check if a service worker still exists or not.
        checkValidServiceWorker(swUrl, config);

        // Add some additional logging to localhost, pointing developers to the
        // service worker/PWA documentation.
        navigator.serviceWorker.ready.then(() => {
          console.log(
            'This web app is being served cache-first by a service ' +
            'worker. To learn more, visit https://bit.ly/CRA-PWA',
          );
        });
      } else {
        // Is not localhost. Just register service worker
        registerValidSW(swUrl, config);
      }
    });
  }
}

function registerValidSW(swUrl, config) {
  navigator.serviceWorker
  .register(swUrl)
  .then(registration => {
    registration.onupdatefound = () => {
      const installingWorker = registration.installing;
      if (installingWorker == null) {
        return;
      }
      installingWorker.onstatechange = () => {
        if (installingWorker.state === 'installed') {
          if (navigator.serviceWorker.controller) {
            // At this point, the updated precached content has been fetched,
            // but the previous service worker will still serve the older
            // content until all client tabs are closed.
            console.log(
              'New content is available and will be used when all ' +
              'tabs for this page are closed. See https://bit.ly/CRA-PWA.',
            );

            // Execute callback
            if (config && config.onUpdate) {
              config.onUpdate(registration);
            }
          } else {
            // At this point, everything has been precached.
            // It's the perfect time to display a
            // "Content is cached for offline use." message.
            console.log('Content is cached for offline use.');

            // Execute callback
            if (config && config.onSuccess) {
              config.onSuccess(registration);
            }
          }
        }
      };
    };
  })
  .catch(error => {
    console.error('Error during service worker registration:', error);
  });
}

function checkValidServiceWorker(swUrl, config) {
  // Check if the service worker can be found. If it can't reload the page.
  fetch(swUrl)
  .then(response => {
    // Ensure service worker exists, and that we really are getting a JS file.
    const contentType = response.headers.get('content-type');
    if (
      response.status === 404 ||
      (contentType != null && contentType.indexOf('javascript') === -1)
    ) {
      // No service worker found. Probably a different app. Reload the page.
      navigator.serviceWorker.ready.then(registration => {
        registration.unregister().then(() => {
          window.location.reload();
        });
      });
    } else {
      // Service worker found. Proceed as normal.
      registerValidSW(swUrl, config);
    }
  })
  .catch(() => {
    console.log(
      'No internet connection found. App is running in offline mode.',
    );
  });
}

export function unregister() {
  if ('serviceWorker' in navigator) {
    navigator.serviceWorker.ready.then(registration => {
      registration.unregister();
    });
  }
}
